Buzz Crowder

Buzz Crowder (played by Ian Wolfe) was an 85 year old WWI veteran who meets with his squad, the 22nd brigade, every 10 years at the Cheers bar; however, he discovers that he is the last surviving member.

It is worth noting that Crowder never appeared in Season 11 (which was ten years after his original appearance). This is due to the fact his actor, Ian Wolfe, died in 1992. Even then, though, it is unlikely the writers would've included another guest appearance by Wolfe as Crowder.